Many industries such as the telecommunication, chemical, pharmaceutical, microelectronic, construction and transportation industries require heated conduit lines for fluids. Some motor vehicles such as trucks and construction equipment in particular involve the need for heated fluid transmission lines especially for vehicles used in cold environments.
Electrically powered heaters have been used which include a metal-sheathed high temperature cable including electrical heating elements separated from the sheath by a mineral insulating material such as powdered magnesium oxide (MgO) or aluminum oxide (Al2O3). Due to the high porosity of the mineral insulator, the cable ends must be hermetically sealed against moisture, especially in a high temperature environment. Ceramic sealed terminations have been proposed to alleviate the risk of moisture seeping into the mineral insulator such as the one disclosed in U.S. Pat. No. 5,917,150 Hampton et al. However, this type of termination provides little thermal isolation to the termination, and is not particularly useful in joining the end of a mineral-insulated heating element to the prong of an electrical connector.
In miniaturized devices where the size of the conduit being heated can be as small as 1 millimeter and where distances are relatively short, heat isolation is very critical. There is a need to effectively and safely connect the end of a mineral-insulated small heating element to a source of electrical power. The instant invention results from efforts to provide an improved thermally isolating hermetic electrical feed-through which addresses one or more of the above problems.